Machine and method for grinding and polishing beads and marbles

ABSTRACT

An apparatus and method for making beads and marbles wherein a bowl is adapted for rotation and has a lower wear plate, and a drag sleeve concentrically disposed within the bowl on a guide shaft and with an upper wear plate disposed opposite the lower wear plate. Balls of a generally spherical shape are placed between the upper and lower wear plates whereby, as weight is placed on the drag sleeve and the bowl is rotated, the balls are ground by a slurry of grit and water between the wear plates.

United States Patent [1 1 [111 33 Kitehel Dec. 9, 1975 [54] MACHINE AND METHOD FOR GRINDING 2,734,317 2/1956 Bond 51/289 S X AND POLISHING BEADS AND MARBLES 3,103,770 /1963 Carter 51/289 S Inventor: George B. Kitchel, 5514 Tupper Lake, Houston, Tex. 77027 Filed: Dec. 9, 1974 Appl. No.: 530,740

U.S.Cl ..5l/7;5l/1ll R;5l/ll7; 51/289 S Int. Cl, B24B 5/18; B24B 1/00 Field of Search 51/7, 117, 118, 111 R, 51/128, 130, 131, 289 S, 317, 318

References Cited UNITED STATES PATENTS 11/1922 Kershaw 51/118 8/1932 Kadzik 51/289 S X ll/l955 Porter 51/131 Primary Examiner-Donald G. Kelly Attorney, Agent, or FirmMurray Robinson; Ned L. Conley; David Alan Rose [57] ABSTRACT An apparatus and method for making beads and marbles wherein a bowl is adapted for rotation and has a lower wear plate, and a drag sleeve concentrically disposed within the bowl on a guide shaft and with an upper wear plate disposed opposite the lower'wear plate. Balls of a generally spherical shape are placed between the upper and lower wear plates whereby, as weight is placed on the drag sleeve and the bowl is rotated, the balls are ground by a slurry of grit and water between the wear plates.

14 Claims, 4 Drawing Figures US. Patent Dec. 9 1975 Sheet 1 of 2 3,924,356

US. Patent Dec. 9 1975 Sheet 2 of2 3,924,356

MACHINE AND METHOD FOR GRINDING AND POLISHING BEADS AND MARBLES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to grinding machines and more particularly relates to apparatus for making beads and marbles.

2. Description of the Prior Art Spherical balls are desired for many purposes, and machines have been built which will make balls to very strict tolerances from almost any material.

A device for grinding balls and polishing them is the Crown Bead Mill (see Crown Lapidary Equipment brochure, pp. 16-17.) This machine consists of a pot or bowl for containing the rough balls between surfaces or plates in an abrasive grit slurry. The pot is mounted on six coil springs and grinding is accomplished by rotating a center shaft which turns an upper plate in the pot while the pot does not rotate.

The idea of balls being ground between two wear plates is disclosed in U.S. Pat. No. 560,940 to Simonds. U.S. Pat. No. 1,772,365 to Pratt discloses a rotating lower grinding disk with a stationary upper disk that has a ball wear groove. Pressure between the disks is accomplished by gravity as shown by U.S. Pat. No. 1,434,824 to Kershaw, and by springs and turnscrews disclosed in U.S. Pat. No. 1,343,011 to Sellew.

The use of such ball grinding machines for polishing balls is disclosed in U.S. Pat. No. 1,516,749 to Moore et al and the Crown Bead Mill. Further the Crown Bead Mill utilizes a separator plate which is inserted between two grinding disks or wear plates to separate the balls as they are being rotated.

The Crown Bead Mill has a main disadvantage. As the center shaft turns rotating the upper disk, the grit and slurry mixture collects in the center due to the spring action and the rotation of the upper disk. Due to the grinding pressure, to the vertical motion due to the mounting springs, and to the centrifugal force caused by the rotating upper disk, the balls collect around the periphery of the pot, and hence are not properly acted upon by the grit and slurry mixture since the mixture collects in the center of the pot and not at the periphery.

Other disadvantages of the Crown Bead Mill are that it cannot dependably produce an even grinding pressure, it is cumbersome, and it cannot be used on a faceting machine thereby limiting its use.

For those interested in collecting rocks for grinding marbles or making beads, the existing ball grinding machines are not suitable. Primarily the existing machinery is too complex and too expensive. Further the grinding surfaces wear out and are difficult to repair or replace.

SUMMARY OF THE INVENTION The present invention includes a bowl-like apparatus which is adaptable for rotation. Inside the bowl a lower wear plate is disposed on the bottom and another upper wear plate is disposed on a drag sleeve opposite the lower wear plate. The drag sleeve is retained so as not to rotate with the bowl and is aligned with the bowl by a guide shaft extending from the center of the bottom of the bowl.

Balls and an abrasive grit slurry are placed between the wear plates. As the bowl is rotated, pressure is 2 placed on the upper wear plate by means of weights or hand pressure and the balls are then ground by the grit slurry.

In the grinding or polishing operations with this invention the rotation of the pot, which contains the slurry and the balls, creates a centrifugal force on the abrasive material in the slurry and on the balls, causing them to move radially outwardly to collect at the periphery so that the slurry maintains contact with the balls throughout the grinding operation.

The apparatus of this invention is simple and inexpensive, yet it provides a highly dependable ball grinding and polishing tool.

Other objects and advantages of the invention will appear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS For a detailed description of a preferred embodiment of the invention, reference will now be made to the accompanying drawings wherein:

FIG. 1 is a partial vertical section of one embodiment of the invention;

FIG. 2 is an enlarged vertical section of the bowl shown in FIG. 1 during grinding operation;

FIG. 3 is an enlarged vertical section of the bowl of FIG. 1 during polishing operation; and

FIG. 4 is an enlarged horizontal section taken through line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 2, there is shown a vertical section of a bead ball grinder during the grinding operation. The bead ball grinder includes a pot 14, a guide shaft 46 concentrically disposed on the bottom surface 28 of pot l4 and extending upwardly therefrom, and a drag sleeve 20 adapted for engagement with the guide shaft 46 and for insertion into pot 14.

Referring to FIG. 1, a drive train 10 rotates pot 14 which is rotatably mounted on table 12. A threaded box 15 is affixed to pot 14 for connection with shaft 18 and arbor 16 comprising a portion of drive train 10. The pot 14 may then be rotated by drive train 10. Drag sleeve 20 is prevented from rotating by retainer clamp 22 disposed on drag sleeve 20 and retainer cord 24 extending from clamp 22 to table 12. The bead grinder is enclosed by a plastic case 26 thereby preventing any splashing from pot 14 as hereinafter described.

The apparatus of this invention may also be operated by the drive motor of a faceting machine (not shown) instead of drive train 10. The bead grinder is connected to the arbor of the faceting machine with an adapter between the pot 14 and the arbor 16. The turntable of the faceting machine is then rotated at 300 to 600 RPM as is suitable for the operation performed.

Because balls 50 do not wear against pot 14, the pot 14 may be cast from a light material such as aluminum or plastic which reduces weight and aids smooth rotation.

Referring again to-FIG. 2, in the preferred embodiment, pot 14 and guide shaft 46 are cast into an integral piece, Guide shaft 46 may also be attached to pot 14 by a threaded engagement between pot 14 and guide shaft 46.

A lower wear plate 40 is disposed on the bottom surface 28 of pot 14. The lower wear plate 40 may be attached to pot 14 by glue, adhesive or screws if desired. An upper wear plate 42 is attached to drag sleeve 20 by means of mounting disk 44. Upper wear plate 42 may be attached to mounting disk 44 by means of screws 48. Wear plates 40 and 42 are replaceable and may be made identical and therefore interchangeable if de sired. The material used for wear plates 40, 42 may vary with the type of balls to be ground in the bead ball grinder and should be of a metal somewhat softer on the Mohs hardness scale than that of balls 50, as for example a steel of hardness S and a ball material of hardness 7. Since wear plates 40, 42 are softer than the balls, grooves will be worn in the plates and they should be replaced as necessary.

Drag sleeve 20 is rotatably and vertically slidably mounted on guide shaft 46 whereby guide shaft 46 concentrically disposes drag sleeve 20 within pot 14. Drag sleeve 20 is made of metal and serves as a weight on the upper wear plate 42. Guide shaft 46 extends upwardly from and is perpendicular to bottom surface 28. Drag sleeve 20 includes a conduit stem 21 for slidingly receiving guide shaft 46. The sliding fit between conduit stem 21 and shaft 46 is so dimensioned as to maintain upper wear plate 42 parallel to lower wear plate 40.

A stop ring 54 circumscribes guide shaft 46 to limit the movement of upper wear plate 42 toward lower wear plate 40. Stop ring 54 must be no thicker than the desired finished diameter of the balls 50 or stop ring 54 will halt the grinding action prematurely.

In the operation of the bead ball grinder, the balls 50 are preformed into crude spheres from glass or stone chunks. Then the crude spheres or balls 50 are placed into pot 14 between lower and upper wear plates 40, 42. An abrasive grit slurry 52 is added to the pot 14 with the balls 50 to create a grinding action. Slurry 52 may comprise about two tablespoons of 80 to 120 mesh carborundum grit, which is a typical initial grit for coarse grinding. Any suitable grinding grit, as well known in the art, may be used. Drag sleeve 20 is slipped over guide shaft 46 until it rests on the balls 50. Restraining clamp 22 is attached to drag sleeve 20 and tied to a stationary point on table 12 by retainer cord 24. Weight disks 56 may be added to drag sleeve 20 to increase the grinding pressure on the balls 50. Additional water may be added to the grit slurry 52. A lid (not shown) may be placed on the pot 14 such that the lid and plastic case 26 keep the grit slurry from splashing. Pot 14 is then rotated by means of drive train and balls 50 are ground to the desired diameter. Usually pot 14 is rotated about 500 RPM to provide an adequate rotation rate for both the grinding operation and the polishing operation hereinafter described.

As the balls 50 are ground, the grit slurry 52 will be changed to consecutively finer meshes until the balls 50 are as desired; e.g., the 80 to 120 mesh carborundum may be replaced with 220 mesh, the 220 mesh replaced by 400 mesh and so on up to a 600 or even finer mesh.

After the balls 50 have been ground to the desired size, they are ready for the polishing operation. In preparing the bead ball grinder for the polishing operation, the grinder is stopped and the drag cord 24 and retainer sleeve 22 are removed. The lid, if any, is taken off and the drag sleeve with mounting disk 44, upper wear plate 42, and any weight disks 56 are lifted up over the guide shaft 46 and removed. The balls 50' and the stop ring 54 are removed and the abrasive grit slurry 52 is cleaned out.

Referring now to FIG. 3, there is shown a vertical section of the bead ball grinder during the polishing operation. Lower wear plate 40 and stop ring 54 are permanently removed from pot 14 since they are not necessary to the polishing operation. A lower leather disk 62 is inserted into pot 14 on bottom surface 28. Upper wear plate 42 is unscrewed from mounting disk 44 and an upper leather disk attached. The upper leather disk 60 is typically attached to mounting disc 44 with a peeloff glue such as Feathering Disc Adhesive manufactured by the 3M Company. The leather disks 60, 62 may be made of other materials suitable for polishing and may be made identical for easy replacement and interchangeability. If desired the leather disks 60, 62 may be attached directly to wear plates 40,42 by any easily removable adhesive.

As shown in FIG. 4 a separator disk 64 of Teflon or other plastic material is placed on the lower leather disk 62. This disk 64 has a plurality of holes 66 for holding and separating balls 50 within pot 14 and a center hole 68 for the insertion over the guide' shaft 46. The thickness of disk 64 must be less than the diameter of balls 50 so that balls 50 may at all times be in contact with both leather disks 60, 62.

In the polishing operation, the balls 50 are placed in the holes 66 and a polishing powder and water are added to the pot 14 and into separator disk 64. Typical suitable polishing powders are any metal oxide, such as aluminum oxide or tin oxide, Linde A powder (ground ruby dust), or cerium oxide. The appropriate powder depends on the hardness and density of the balls 50. The drag sleeve 20 with mounting disk 44, upper leather disk 60, and any necessary weight disks 56 are slipped over guide shaft 46. Retainer sleeve 22 and retainer cord 24 are then attached. Additional water may be added to the polishing powder. The lid may be placed on the pot 14 to keep the polishing slurry from splashing out. The pot 14 is then rotated and the balls polished until the desired finish is reached. The polishing operation normally lasts one to two hours.

While a preferred embodiment of the invention has been shown and described, modification thereof can be made by one skilled in the art without departing from the spirit of the invention. The invention is not, therefore, limited to the specific embodiment shown and described, but only as defined by the accompanying claims.

I claim:

1. A machine for grinding balls comprising:

bowl means for containing the balls having a bottom surface and being adaptable for rotation;

a guideshaft concentrically disposed on said bottom surface of said bowl means;

a non-rotating member slidably engaging said guideshaft, said guideshaft aligning said non-rotating member within said bowl means; and

said non-rotating member having a non-rotating surface oppositely disposed to said bottom surface, said non-rotating surface being perpendicular to the axis of rotation of said bowl means.

2. A machine for grinding balls as defined in claim 1 and including a first wear plate disposed on said bottom surface of said bowl means; and

a second wear plate disposed on said non-rotating surface; the balls being inserted between said first and second wear plates for grinding.

3. A machine for grinding balls as defined in claim 2 and including weight means for'pressing said second wear plate toward said first wear plate.

4. A machine for grinding balls as defined in claim 3 and including stop means to limit the movement of said second wear plate toward said first wear plate.

5. A machine for grinding balls as defined in claim 4 and including abrasive means for creating a grinding action with the balls.

6. A machine for grinding balls as defined in claim 3 and including separation means to separate the balls; and polishing material affixed to said wear plates.

7. A machine for grinding balls to a finished diameter as defined by claim 6 wherein said separation means includes a separation disk containing a plurality of holes for insertion of the balls, said separation disk having a thickness less than the finished diameter of the balls.

8. A machine for grinding balls comprising;

a pot adapted for rotation having a bottom surface;

rotation means to rotate said pot;

a guideshaft concentrically disposed on said bottom surface and extending vertically upward;

a first wear plate disposed on said bottom surface;

a drag sleeve slidably mounted on said guideshaft, said guideshaft positioning said drag sleeve within said pot;

retention means to prevent said drag sleeve from rotating; and

a second wear plate affixed to said drag sleeve and facing said first wear plate.

9. A machine for grinding balls as defined in claim 8 including:

weight means disposed on said second wear plate;

and

stop means to maintain a minimum distance between said first and second wear plates.

10. A machine for polishing balls comprising:

a pot adapted for rotation having a bottom surface;

rotation means to rotate said pot;

a guide shaft concentrically disposed on said bottom surface and extending vertically upward;

a first polishing disk disposed on said bottom surface;

separation means for holding and separating the balls; said separation means including a disk having a plurality of holes and disposed on said first polishing disk and around said guideshaft;

a drag sleeve slidably mounted on said guideshaft and including a second polishing disk affixed to said drag sleeve to face said first polishing disk, said guideshaft positioning said drag sleeve within said pot; and

retention means to prevent said drag sleeve from rotating.

11. A machine for polishing balls of a finished diameter as defined in claim 10 wherein:

said first and second polishing disks are attached by an adhesive;

said first and second polishing disks being of any of a group of materials consisting of leather, felt, or other suitable polishing material;

said separation disk being composed of any of the group consisting of leather, teflon, or other soft plastic material, and

said separation disk having a thickness less than the finished ball diameter.

12. A method for grinding balls comprising:

insertion of pre-formed roughly spherical balls into a pot adapted for rotation:

adding a slurry of grinding grit and water to the' balls;

placing an upper wear plate disposed opposite the bottom of the pot and on a guideshaft concentrically disposed from the bottom of the pot;

grinding the balls by rotating the pot while preventing the upper wear plate from rotating; and

maintaining the balls and the slurry at the periphery of the pot by placing a centrifugal force created by the rotation of the pot on both the balls and the slurry causing them to collect at the periphery of the pot.

13. A machine for grinding balls in a slurry comprisa pot adapted for rotation having a bottom surface;

a guideshaft concentrically disposed on said bottom surface of said pot and extending vertically from said bottom surface;

a non-rotating member disposed on said guideshaft;

said non-rotating member having a surface oppositely disposed to said bottom surface;

said non-rotating member surface being perpendicular to the axis of rotation of said pot and aligned by the guideshaft so that it is parallel to said bottom surface of said pot; and means for maintaining the balls and slurry at the periphery of said pot.

14. A machine for grinding balls in a grit slurry comprising:

a pot having a bottom surface;

a member disposed within said pot whereby the balls and grit slurry are disposed between said member and said bottom surface;

means for creating a force on the balls and grit slurry causing the balls and grit slurry to move toward the periphery of the pot as said pot is rotated; and

means for maintaining the balls and the grit slurry at the periphery of said pot. 

1. A machine for grinding balls comprising: bowl means for containing the balls having a bottom surface and being adaptable for rotation; a guideshaft concentrically disposed on said bottom surface of said bowl means; a non-rotating member slidably engaging said guideshaft, said guideshaft aligning said non-rotating member within said bowl means; and said non-rotating member having a non-rotating surface oppositely disposed to said bottom surface, said non-rotating surface being perpendicular to the axis of rotation of said bowl means.
 2. A machine for grinding balls as defined in claim 1 and including a first wear plate disposed on said bottom surface of said bowl means; and a second wear plate disposed on said non-rotating surface; the balls being inserted between said first and second wear plates for grinding.
 3. A machine for grinding balls as defined in claim 2 and including weight means for pressing said second wear plate toward said first wear plate.
 4. A machine for grinding balls as defined in claim 3 and including stop means to limit the movement of said second wear plate toward said first wear plate.
 5. A machine for grinding balls as defined in claim 4 and including abrasive means for creating a grinding action with the balls.
 6. A machine for grinding balls as defined in claim 3 and including separation means to separate the balls; and polishing material affixed to said wear plates.
 7. A machine for grinding balls to a finished diameter as defined by claim 6 wherein said separation means includes a separation disk containing a plurality of holes for insertion of the balls, said separation disk having a thickness less than the finished diameter of the balls.
 8. A machine for grinding balls comprising; a pot adapted for rotation having a bottom surface; rotation means to rotate said pot; a guideshaft concentrically disposed on said bottom surface and extending vertically upward; a first wear plate disposed on said bottom surface; a drag sleeve slidably mounted on said guideshaft, said guideshaft positioning said drag sleeve within said pot; retention means to prevent said drag sleeve from rotating; and a second wear plate affixed to said drag sleeve and facing said first wear plate.
 9. A machine for grinding balls as defined in claim 8 including: weight means Disposed on said second wear plate; and stop means to maintain a minimum distance between said first and second wear plates.
 10. A machine for polishing balls comprising: a pot adapted for rotation having a bottom surface; rotation means to rotate said pot; a guide shaft concentrically disposed on said bottom surface and extending vertically upward; a first polishing disk disposed on said bottom surface; separation means for holding and separating the balls; said separation means including a disk having a plurality of holes and disposed on said first polishing disk and around said guideshaft; a drag sleeve slidably mounted on said guideshaft and including a second polishing disk affixed to said drag sleeve to face said first polishing disk, said guideshaft positioning said drag sleeve within said pot; and retention means to prevent said drag sleeve from rotating.
 11. A machine for polishing balls of a finished diameter as defined in claim 10 wherein: said first and second polishing disks are attached by an adhesive; said first and second polishing disks being of any of a group of materials consisting of leather, felt, or other suitable polishing material; said separation disk being composed of any of the group consisting of leather, teflon, or other soft plastic material, and said separation disk having a thickness less than the finished ball diameter.
 12. A method for grinding balls comprising: insertion of pre-formed roughly spherical balls into a pot adapted for rotation: adding a slurry of grinding grit and water to the balls; placing an upper wear plate disposed opposite the bottom of the pot and on a guideshaft concentrically disposed from the bottom of the pot; grinding the balls by rotating the pot while preventing the upper wear plate from rotating; and maintaining the balls and the slurry at the periphery of the pot by placing a centrifugal force created by the rotation of the pot on both the balls and the slurry causing them to collect at the periphery of the pot.
 13. A machine for grinding balls in a slurry comprising: a pot adapted for rotation having a bottom surface; a guideshaft concentrically disposed on said bottom surface of said pot and extending vertically from said bottom surface; a non-rotating member disposed on said guideshaft; said non-rotating member having a surface oppositely disposed to said bottom surface; said non-rotating member surface being perpendicular to the axis of rotation of said pot and aligned by the guideshaft so that it is parallel to said bottom surface of said pot; and means for maintaining the balls and slurry at the periphery of said pot.
 14. A machine for grinding balls in a grit slurry comprising: a pot having a bottom surface; a member disposed within said pot whereby the balls and grit slurry are disposed between said member and said bottom surface; means for creating a force on the balls and grit slurry causing the balls and grit slurry to move toward the periphery of the pot as said pot is rotated; and means for maintaining the balls and the grit slurry at the periphery of said pot. 